2. Place the lamb on a chopping board and make several slits all over the joint. Mix together the orange zest, garlic, the leaves from the rosemary sprigs, removed from the stalk and the oil. Season.

3. Stuff the mixture into the slits. Place on a metal rack in a roasting tin and open roast for the preferred calculated cooking time. From time to time during cooking continue to baste the joint with the lamb juices from the roasting tin.

4. 10-15 minutes before the end of the cooking time glaze the joint with the orange marmalade.

5. Remove the joint from the oven, wrap loosely in foil and allow to rest for 10-15 minutes.

6. To make the gravy, place the roasting tin on the hob, skim off any surface fat and discard, leaving the rich lamb juices. Increase the heat and stir in the flour. Add the water and orange juice, bring to the boil, reduce the heat and simmer, stirring occasionally, for about 8 minutes until thickened and glossy.

7. Pour any lamb juices from the joint into the gravy, season and serve the lamb with the gravy, new or roasted potatoes and seasonal vegetables.